no-start problem

[Flynlow]

Hello everyone,

I was hoping I could lean on this forums' experience to diagnose my car's trouble.

The vehicle is a 1990 325i. The car drove home fine and had been trouble free up to that point, however the next morning it refused to start. It cranks, but won't run.

Steps taken so far:

-Pulled a spark plug, grounded to the head, and cranked. Sparks fine.
-There was an aftermarket alarm system on the car from a PO, it was clicking under the dash. I removed it completely and set the wiring back to OEM (I abhor alarm systems).
-The shielding had come off the CPS sensor and a wire was exposed. I replaced the sensor with a new one from PelicanParts.
-I jumped the fuel relay and the pump kicked on very audibly. Still wouldn't start though.


Anyone have any other ideas? I appreciate any and all assistance. Thanks!

[jlevie]

If you have spark the DME is getting a timing reference signal. That would suggest a problem with the fuel pump relay of the pump. Your statement that the "pump kicked on very audibly" when jumped would tend to make me think that the pump is bad or about to fail, since it should barely be audible. But I would try replacing the fuel pump relay since it sounds like the pump may not be running when the engine is cranking.

[Flynlow]

Is it possible the CPS sensor going bad could have affected something else on the car?

[jlevie]

I'd say that it would be unlikely for damage to the CPS or its wiring to have affected the DME, but it is possible. However, if that happened the DME would not be getting the timing reference data and would not be firing the plugs. So that probably isn't your problem.

Does the fuel pump run when the car is being cranked? And if so what pressure is present at the input to the fuel rail? If the pump doesn't run the fuel pump relay is a likely candidate. If the pump runs you have to find out if it is producing enough pressure, hence the pressure check.

[Flynlow]

If the fuel pump relay is manually jumped, shouldn't the car start then?

[Flynlow]

Just to bring some closure to this thread for anyone who might have a similar problem, it was the relay :).

[homegrone30]

i had the same problem on my es but the real was an abs voltage protection relay or some shit located under the dash on the drivers side

[delphini]

homegrone please explain ? was this a fuse or a relay and how did you resolve these issues ?